There are known drivers applied for power converters that are equipped with series-connected upper- and lower-arm switching elements, such as IGBTs, connected in parallel to a direct-current power source. The upper- and lower-arm switching elements are also known as high- and low-side switching elements. In such a power converter, while there is a short-circuit fault in one of the upper- and lower-arm switching elements, turn-on of the other thereof causes the upper- and lower-arm switching elements to be short-circuited, which causes an overcurrent to flow through the upper- and lower-arm switching elements.
Technologies for protecting an IGBT as an example of switching elements against such an overcurrent are known, one of which is disclosed in Japanese Patent Application Publication No. H05-218836. A driver disclosed in the Patent Publication is equipped with an overcurrent protection circuit. Specifically, the driver is equipped with a series connection comprised of a bipolar transistor and a Zener diode connected in series to each other, and the series connection is connected between the gate and emitter of the IGBT. The bipolar transistor is switched from an off state to an on state when it is determined that an overcurrent is flowing through the IGBT. The turn-on of the switching element limits the gate voltage of the IGBT to a predetermined Zener voltage of the Zener diode, thus reducing the gate voltage of the IGBT. This suppresses the overcurrent flowing through the IGBT.